Earth's History Crossword

The process in which a radioactive isotope tends to break down into a stable isotope of the same element or another element
States that layers of sedimentary rocks, younger rocks normally lie on top of older rocks if the layers have not been disturbed
Any method of measuring the age of an event or object in years
Atom of a substance that has the same number of protons but a different number of neutrons as another atom of the same substance
Fossilized mark that formed in sedimentary rock by the movement of an animal on or within soft sediment
Very long period of time the Earth has existed
Break in the geologic record created when rock layers are eroded or sediment is not deposited for a long period of time
Idea that geologic processes that occurred in the past can be explained by current geologic processes
Method of determining the absolute age of an object by comparing the relative percentages of a radioactive parent isotope and a stable daughter isotope
Amount of time required for half of an original sample of radioactive material to decay or undergo radioactive transformation
Any method of determining whether an event or an object is older or younger than other events or objects
Stable element into which a radioactive element breaks down
Remains or traces of past plants or animal life that has been preserved in sedimentary rock
Fossil that is used to establish the age of a rock layer because the fossil is distinct, abundant, and widespread, and the species that formed the fossil existed for only a short span of geologic time
A historical sequence of life indicated by fossils found in layers of the Earth's crust